1. Field of the Invention
The invention relates to a technology for storing abnormality diagnostic data used for diagnosing an abnormality in correspondence with the abnormal event of an abnormality when the abnormality is detected in a vehicle.
2. Description of the Background
When an abnormality occurs in a vehicle, it is preferable to store necessary data for diagnosing the abnormality.
When an abnormality occurs in a vehicle, an abnormality diagnostic system judges the abnormality and stores main data (e.g., data showing behavior of the vehicle such as engine cooling water temperature), at the time when the abnormality occurred, as abnormality diagnostic data, i.e., freeze-frame data. Whenever an abnormality occurs, this freeze-frame data is stored separately for each of the abnormal events. Types and the number of stored data are fixed irrespective of a difference in the abnormal events.
In recent years, as the complexity of control systems in vehicles has increased due to greater use of electronic circuits, the difficulty level of analysis of an abnormal event drastically rises. Further, in the case of an abnormal event related to faulty soldering in an electronic circuit, generation of the abnormality can be inconsistent depending upon the temperature of the substrate, which makes it difficult to reproduce that abnormal event.
For example, Japanese Patent Application Laid-Open Publication No. HEI 5-171998 discloses a related technology as an abnormality diagnostic system of this kind. However, in this abnormality diagnostic system, the types and the number of freeze-frame data stored whenever an abnormal event occurs are set irrespective of a difference in the abnormal events. Therefore, when an abnormality diagnosis is carried out later using such freeze-frame data, although the behavior or state of the vehicle when an abnormality occurs can be grasped from the freeze-frame data, it is extremely difficult to analyze and reproduce the abnormal event which occurred. Thus, there is no usable method except one of listing potential possibilities from the freeze-frame data and then estimating inappropriate one of the listed possibilities by a process of elimination.